BGP works

[Cai, Land -CN-IT]

Hello, Dear friends,     I am studying BGP. Says on book, when the routing policy that will be implemented in the autonomous system is consistent with policy implemented in the ISP autonomous system, the BGP can be replaced by a combination of static routes and default networks, while any time your policy requirements differ from the policy of your ISP, BGP is required. I really don¡¯t know under which situation we can say have the same routing policy with ISP. Can you give me a specific example?     Thanks